1. FIELD OF THE INVENTION
The present invention relates to an exercise machine in which the resistance experienced by a user can be varied dynamically under the control of the user or an instructor.
2. DESCRIPTION OF THE PRIOR ART
In weight training, exercises involve the movement of a body part subject to an externally applied resistance. The exercise itself is the movement of a body part through a predetermined range of motion, which is also referred to herein as the movement. To enhance muscular development an external force is applied to the body part during the execution of the movement. In other words, an external resistance must be overcome for the movement to be executed.
The exercise routine or exercise program is generally broken up into sets. Each set consists of executing several repetitions of the movement or exercise. A period of rest follows each set after which the subsequent set is performed. The number of repetitions in each set is determined by the limit of endurance of the person performing the exercise.
To maximize muscular development and strength gains, athletes perform what are known as forced repetitions. Near the end of the set, the muscles stored energy reserves become depleted, and as a result, the force generated by the muscle is reduced compared to a rested muscle. Therefore, the athlete may not be able to execute the movement after a certain number of repetitions. When an athlete reaches this point, he or she forces himself or herself to perform a few extra repetitions which cannot be performed without some assistance from another person referred to as a "spotter". These extra repetitions are known as "forced repetitions" and help to maximize muscular hypertrophy.
The problem with using a spotter is that the athlete has to schedule workouts at times that are convenient for both the athlete and the spotter. Therefore, the need for a spotter reduces the athlete's freedom and flexibility in scheduling the athlete's workouts, and can lead to a reduction in the athlete's opportunities to workout. The exercise machine of the present invention has been developed to obviate the need for a spotter and thus allow the athlete to work out whenever it is convenient for him or her. Further, the exercise machine of the present invention allows a coach or instructor to vary the resistance against which the athlete is working while observing the athlete during the performance of the exercise.
Although a dynamically variable resistance exercise machine is known in the prior art, none of the prior art show the electromechanical variation of the resistance by varying the moment arm of a weight moved along a pivoting arm under the impetus of an electric motor.
U.S. Pat. No. 4,231,568, issued to Robert Q. Riley et al. on Nov. 4, 1980, shows an exercise machine where the movement performed by the user is resisted by springs. The force exerted by the user is applied to the springs through a cam arrangement which ensures that constant force is applied by the user throughout the range of motion characteristic of the particular exercise. Riley et al. do not use an electric motor to move a weight along a pivoting arm.
U.S. Pat. No. 4,509,746, issued to Ernest D. Mask on Apr. 9, 1985, shows a leg exercise bench that converts from a first configuration to a second configuration. The first configuration allows the user to be in a seated posture and perform leg exercises that are normally performed in the seated posture. The second configuration allows the user to be in a prone posture and perform leg exercises that are normally performed in the prone posture. Mask does not use an electric motor to move a weight along a pivoting arm.
U.S. Pat. No. 5,088,726, issued to Thomas G. Lapcevie on Feb. 18, 1992, shows an exercise apparatus in which the user exercises by applying a torque to a cam. A cable attached to the cam is routed through several pulleys and supports a stack of weights. The user's performance of the exercise causes the cam to rotate, lifting the stack of weights via the cable. The resistance experienced by the exerciser during the execution of the exercise varies in accordance with the profile of the cam to which the cable pulling the stack of weights is attached. Therefore by choosing the cam profile, any desired variation in resistance during the execution of the exercise can be obtained. Lapcevie does not use an electric motor to move a weight along a pivoting arm.
U.S. Pat. No. 5,356,360, issued to George Johns on Oct. 18, 1994, shows a weight training machine with a variable resistance cam, where the exercise is accomplished by causing a lever arm to pivot. The lever arm is adjustable, and the lever arm adjustment mechanism is designed so that the variable resistance force is not affected by the starting position of the lever arm. Johns does not use an electric motor to move a weight along a pivoting arm.
U.S. Pat. No. 5,387,170, issued to R. Lee Rawls et al. on Feb. 7, 1995, shows a weight training machine wherein the user moves a weight via a pivot arm moving through a pivot arm plane. The angular orientation of the pivot arm plane is user selectable and determines the resistance force experienced by the user. Rawls et al. do not use an electric motor to move a weight along a pivoting arm.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.